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According to the FAR's if fir is up to spec it can be used in any area that
spruce is used.
Wing ribs?
From what I remember, (if that is right) douglas fir of the same
dimentions, is heavier, and slightly stornger than spruce.

Fir is about 25% heavier and about 21% stronger than Sitka Spruce.
I am just wondering in which areas of construction douglas fir could be
used, whithout violating some reasonable conventions of safety. And also
just how much you would save in money and gain in weight, if you used as
much douglas fir as would be resonable. Its just that spruce seems so

Cost savings varies, but if you can find a good deal on fir it can save you
up to 80%.

Gordon Nichol
Steve Eldredge

Some years ago, I built a Corben Jr. Ace. Open cockpit, fabric covered sport plane from 1929. I read everything the EAA had on wood and wood substitutions. In the end, I found my local lumber yard had some terrific Doug Fir in long lengths with tight, straight running grain.
I used it for the spars, I ripped it into the 1/4" x 1/4" strips I needed to build the ribs and everything else where Sitka was called for.
The FAA inspector told me it was way better than almost all the Sitka he's seeing these days.
Go ahead and use it.
Brian
Michigan

According to the FAR's if fir is up to spec it can be used in any area that
spruce is used.
Wing ribs?
From what I remember, (if that is right) douglas fir of the same
dimentions, is heavier, and slightly stornger than spruce.

Fir is about 25% heavier and about 21% stronger than Sitka Spruce.
I am just wondering in which areas of construction douglas fir could be
used, whithout violating some reasonable conventions of safety. And also
just how much you would save in money and gain in weight, if you used as
much douglas fir as would be resonable. Its just that spruce seems so

Cost savings varies, but if you can find a good deal on fir it can save you
up to 80%.

Gordon Nichol
Steve Eldredge

Some years ago, I built a Corben Jr. Ace. Open cockpit, fabric covered sport plane from 1929. I read everything the EAA had on wood and wood substitutions. In the end, I found my local lumber yard had some terrific Doug Fir in long lengths with tight, straight running grain.
I used it for the spars, I ripped it into the 1/4" x 1/4" strips I needed to build the ribs and everything else where Sitka was called for.
The FAA inspector told me it was way better than almost all the Sitka he's seeing these days.
Go ahead and use it.
Brian
Michigan
Just make sure it meets all the other requirements - good close
straight grain etc.